With an expanded capacity minicomputer, simulation and analysis of protein sequence evolution will continue. Further tests of distance estimating algorithms and statistical tests of the "molecular clock" hypothesis will be completed. As indicated in the original grant proposal, a number of well-defined statistical artifacts tend to bias conventional analysis toward apparent regularity of evolutionary rates. These biases will be documented and ways of compensation tested. Testing of, and possible improvement of, tree-making algorithms remains a goal for the coming year. Further work on the charge-state model of protein variation is in progress and will be completed; specifically, a detailed comparison of predicted distributions with real electrophoretic data will be completed and published. Manuscripts on population variation already accepted for publication will be revised. Several smaller, related programs are in progress. One of these involves simulation of a diploid population of 1000 one-locus individuals subject to mutation, environmental variation and quasi-threshold selection. It appears that genetic variance at equilibrium is inversely proportional to environmental variance, which is in accord with published observations of electrophoretic variation in real populations, where species living in relatively constant environments have relatively high levels of polymorphism. This work will be completed and published, and possibly extended. BIBLIOGRAPHIC REFERENCES: King, J.L., and T Ohta. Polyallelic mutational equilibria. Genetics 79:681-691, 1975. King, J.L. The genetic basis of evolutionary change (book review). Annals of Human Genetics 38: 507-509, 1975.